Central valve for a camshaft adjuster having central locking

ABSTRACT

A central valve ( 1 ) for a camshaft adjusting device including a control piston ( 2 ) having a first ( 3 ) and a second ( 4 ) control edge which enclose a first annular groove ( 6 ), including a valve housing ( 26 ), on the peripheral wall of which openings ( 14, 15, 16, 17, 18 ) are disposed, and including pressure medium paths extending between a feed connection and a discharge connection P, T of which the adjustable configuration is predetermined by the control edge geometry and the arrangement of the openings ( 14, 15, 16, 17, 18 ) and the adjusted configuration is dependent upon the relative axial position of the control piston ( 2 ).

The present invention is in the field of proportional way valves whichmay be used, in particular, for controlling so-called camshaftadjusters. Camshaft adjusters are used to regulate the operation of aninternal combustion engine by influencing the charge cycle in a targetedmanner: An adjustment of the phase angle of the camshaft changes theposition thereof in relation to the phase angle of the crankshaft; theopening and closing times of gas exchange valves may thus be shifted toan earlier or later point in time of the completed cycle. Central valveshave multiple switching positions, with the aid of which the profile ofa pressure medium path between an inlet and an outlet may be set—thepressure medium flow applies a force to the camshaft adjuster, which isdependent on the switching position and causes an adjustment into acertain position.

BACKGROUND

DE 10 2012 201 567 A1 shows a central valve of a camshaft adjuster ofthis type. The inflow takes place via a radial bore in the camshaft andsupplies the central valve with pressure medium via its camshaft-sideend. The outflow takes place via a radial bore on the valve housing. Forthe purpose of control, the central valve has two supply ports, with theaid of which a connection may be established between an inlet port and aworking chamber of the camshaft adjuster. Refinements of camshaftadjusters of this type include additional features, for example alocking piston, which is able to mechanically fix the moving elements ofthe adjuster. Another supply port and an additional switching positionare necessary—i.e., an extension of the central valve, with the aid ofwhich the locking piston may be driven. One disadvantage is theelongation of the control valve following a conventional extension,which affects the required installation space.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a central valve,which has a simple structure and enhanced functionality, andsimultaneously optimizes the required installation space.

Accordingly, a central valve for a camshaft adjusting device is claimed,which includes a control piston, which has a first and a second controledge, which encompass a first annular groove, a valve housing, on whosecircumferential wall openings are arranged, as well as pressure mediumpaths, which run between an inlet and an outlet port P, T and whosesettable profile is predefined by the control edge geometry and thearrangement of the openings and whose set profile depends on therelative axial length of the control piston.

Moreover—with respect to a central position of the control piston—thefirst control edge is assigned to a first opening and is designed tohave a negative overlap with respect to the first opening in such a waythat the first control edge does not cover the first opening on the sidefacing the second control edge, while the first control edge just closesthe first opening—which transitions to an annular channel on the valvehousing side—on the side facing away from the second control edge, andthe second control edge is assigned to a second opening and just closesthe latter on its side facing the first control edge, a third openingbeing assigned to the first opening, situated at an offset in thecircumferential direction, and the first control edge, which is designedto have a positive overlap with respect to the third opening, justcompletely closing the third opening on the side facing the secondcontrol edge.

According to the finding of the present invention, the assignment of acontrol edge to its corresponding opening—which is considered to berequired in conventional approaches—may be eliminated. Due to aningenious arrangement of openings along the circumference, a pressuremedium path is interrupted even in the case that a control edge does notcover or even completely unblocks its corresponding opening. While thepressure medium enters the area of the annular groove of the controlpiston via the unblocked opening, a through-flow is neverthelesssuppressed in that no additional openings are unblocked. With the aid ofthe proposed invention, a shortening of the control edge unblocking theparticular opening is facilitated. The central valve may thus performadditional functions and be simultaneously optimized with regard to itsaxial installation space requirements.

In one preferred specific embodiment, the first and second control edgesare followed by a third control edge, which encompasses a second annulargroove together with the second control edge, a fourth opening beingsituated at an axial offset from the first and third openings and afifth opening from the first, second and third openings. The specificembodiment thus claimed describes a central valve which is suitable fora design as a proportional 4/5-way valve.

According to another preferred specific embodiment, the fourth openingis situated at an offset in relation to the third opening in the axialdirection in such a way that the second control edge, which is designedto have a positive overlap with respect to the fourth opening, justcompletely unblocks the fourth opening on the side facing the thirdcontrol edge. A positive control edge overlap means that the height ofthe control edge is greater than the width of the opening. The advantageof this specific embodiment is that it minimizes the necessary lengthsof the first and second control edges.

In another preferred specific embodiment, the second and third controledges are designed to have a zero overlap with respect to the second andfifth openings, respectively, so that they close the second and fifthopenings, respectively. This specific embodiment also has the advantagethat the necessary length of the control edges is minimized. A zerooverlap is present when the control edge terminates flush with theopening. A control edge geometry which does not terminate completelyflush should also be viewed as a zero overlap. The stationary behaviorof a camshaft adjuster is influenced by throttling the outflow in atargeted manner, whereby additional functions are made possible.

According to one advantageous specific embodiment, a supply port A isconnected to the second opening, a supply port C is connected to thethird and fourth openings, and a supply port B is connected to the fifthopening—facing outwardly in each case. The design for a proportional4/5-way valve may be created in this way, which has proven to beadvantageous to the driving of a camshaft adjuster. A design having asupply port C has proven to be particularly favorable. The camshaftadjuster may thus be driven independently of its working chambers.

In another advantageous embodiment, a pressure medium path betweensupply port C and outlet port T may be formed via the third opening, anda pressure medium path between supply port C and inlet port P may beformed via the fourth opening, the first opening transitioning to theannular channel, with the aid of which supply port A may be connected toan outlet port T. The claimed specific embodiment has proven to beparticularly advantageous for driving camshaft adjusters which areequipped with locking pistons. Locking pistons of this type areparticularly suitable, in particular, for fixing the relatively movableelements of the adjuster, particularly into an intermediate position.The proposed design of supply port C ensures that the locking piston isconnected to either inlet or outlet port P, T.

According to one preferred specific embodiment of the central valve, ina first switching position, supply ports A and C are connected to inletport P, and supply port B is connected to outlet port T, while, in asecond switching position, supply port C is connected to inlet port P,and supply ports A and B are blocked by a control edge; in a thirdswitching position, supply ports B and C are connected to inlet port Pand supply port A is connected to outlet port T, while in a forthswitching position, supply port C is connected to outlet port T andsupply port B is connected to inlet port P and supply port A is blockedby a control edge. A design of the central valve having a correspondinggeometry of the control edges is advantageous for implementing aparticular switching logic, which is suitable for controlling a camshaftadjuster having central locking.

One advantageous refinement is thus to use the central valve in acamshaft adjusting device, which includes a rotor which is coaxially androtatably situated in relation to a stator, and which includes at leastone locking piston C, with the aid of which the position of the rotor inrelation to the stator may be fixed in a defined position.

The central valve is preferably used to control a vane adjuster. Vaneadjusters include a stator and a rotor as essential elements. The statoris rotatably fixedly connected to a drive wheel and is driven by thecrankshaft via a traction mechanism drive. The rotor forms the outputelement.

The rotor is situated concentrically to the stator and is surroundedthereby. An indentation is situated in the stator in the circumferentialdirection, which is closed to form a pressure-tight cavity—withoutinterfering with the mobility between the rotor and stator in thecircumferential direction: laterally by a cover or by a side wall and onthe inner diameter by the outer circumferential wall of the rotor. Avane, which is fixedly connected to the rotor and divides the cavityinto two pressure-tightly closeable chambers A and B, engages with thecavity.

By connecting pressure chambers A and B to either inlet port P or outletport T in a targeted manner, a pressure difference may be generated,whereby a force acts upon the vane. The vane is thus displaced in thecircumferential direction together with the rotor.

The displacement of the rotor results in a change in the phase angle ofthe camshaft in relation to the phase angle of the crankshaft: If thecamshaft rotates in the clockwise direction, and if pressure chamber Bmoves ahead of pressure chamber A, an adjustment of the vane in thedirection of pressure chamber B causes an adjustment of the opening andclosing times toward an earlier point in time. The phase angle of therotor relative to the stator may be mechanically fixed in a definedposition with the aid of locking piston C.

A specific embodiment is particularly preferred, in which the centralvalve is able to communicate with pressure chambers A and B of thecamshaft adjusting device via supply ports A and B and with the at leastone locking piston C via supply port C, and the at least one lockingpiston C is unlocked as a result of an application of pressure medium.The advantage of the specific embodiment is its switching logic, whichis achievable with the aid of the claimed central valve, supply port Cis connected to outlet port T only in the fourth switching position,whereby locking piston C is able to enter a locking gate andmechanically fixes the relatively movable elements of the camshaftadjuster.

According to one refinement of the central valve, the third control edgeis followed by a fourth control edge, which encompasses a third annulargroove together with the third control edge, a sixth opening beingassigned to the third control edge. The advantage of this specificembodiment is that additional switching positions may be added to theclaimed central valve. In particular, a proportional 5/5-way valve maythus be implemented.

The present invention is now explained in greater detail on the basis ofone exemplary embodiment, reference being made to the drawing.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 shows a sectional view of a control valve in a central housing.

DETAILED DESCRIPTION

FIG. 1 shows a central valve 1 including a control piston 2, whosedepicted central position is clearly illustrated for the control edgegeometry characteristic for the present invention. Control piston 2includes a first, second and third control edge 3, 4, 5 as well as afirst and a second annular groove 6, 7. Control piston 2 also has ahollow design, so that a pressure medium may pass through a controlpiston cavity 8. Inlet and outlet openings are provided on both ends forthis purpose. In the illustrated specific embodiment, a front opening issituated at a first end 9, and additional openings are situated at asecond end 10. The openings at second end 10 are arranged along thecircumference of a piston head 11 (piston head openings 12), which has areduced diameter with respect to the control edge sections.

Control piston 2 is axially displaceably guided in a guiding sleeve 13.Guiding sleeve 13 has a first to fifth opening(s) (14, 15, 16, 17, 18),which is/are situated at an offset. The first and third openings aresituated at an offset in the circumferential direction.

Guiding sleeve 13 is extrusion-coated with plastic (plasticextrusion-coating 19). Openings are also situated on plasticextrusion-coating 19, which facilitate the transfer of the pressuremedium between central valve 1 and a camshaft adjuster (not illustrated)surrounding central valve 1 (transfer opening): first through fourthtransfer opening(s) (20, 21, 22, 23). Plastic extrusion-coating 19additionally forms a spring seat 24 for a spring 25, whose force actsupon first end 9 of control piston 2.

Control piston 2 is inserted into a central housing 26, together withguiding sleeve 13 and plastic extrusion-coating 19. Within centralhousing 26, plastic extrusion-coating 19 is supported on a contactsurface 27. A sleeve, which includes a check valve 27 a, is alsoprovided between plastic extrusion-coating 19 and central housing 26. Aretaining ring 28 is situated on the opposite side for fixing purposes.A flange 29 is provided on central housing 26, which aligns and supportscentral valve 1 in a cavity of a camshaft (not illustrated), whichaccommodates central valve 1.

Openings which facilitate the transfer of the pressure medium betweenthe central valve and a camshaft adjuster (housing openings) are alsosituated on central housing 26; the housing openings form supply portsA, B and C as well as inlet and outlet ports P and T.

-   -   Supply port A is connected to second opening 15 via second        transfer opening 21;    -   Supply port B is connected to fifth opening 18 via fourth        transfer opening 23;    -   Supply port C is connected to third and fourth openings, 16, 17        via third transfer opening 22; in principle, the third and        fourth openings may also be connected to separate housing        openings;    -   First transfer opening 20 is connected to first opening 14.        First transfer opening 20 is closed on the housing side and thus        forms an annular channel, which unblocks a pressure medium path        for the pressure medium from supply port A to outlet port T via        first annular groove 6, first transfer opening 14 as well as        control piston cavity 8 and piston head openings 12.

In the illustrated central position,

-   -   third control edge 5 covers fifth opening 18, so that supply        port B is blocked. Third control edge 5 is designed to have a        zero overlap with respect to fifth opening 18—the control edge        terminates flush with the opening;    -   second control edge 4 covers second opening 15, so that supply        port A is blocked. Second control edge 4 is also designed to        have a zero overlap;    -   first control edge 3 covers third opening 16, second control        edge 4 just unblocking fourth opening 17, so that supply port C        may be connected to inlet port P via second annular groove 7.

A displacement of control piston 2 in the direction of first end 9unblocks third opening 16; first control edge 3 must therefore closefirst opening 14 on its side facing away from second control edge 4 sothat supply port C is not simultaneously connected to inlet port P andoutlet port T. Moreover, supply port A is connected to inlet port P, andsupply port B is connected to outlet port T. First control edge 3 isthus designed to have a negative overlap with first opening 14; thecontrol edge height is therefore less than the width of the opening. Bydisplacing control piston 2 in the direction of second end 10, fourthopening 17 is closed with the aid of second control edge 4, and thirdopening 16 is unblocked on the side facing away from first annulargroove 6. The height of first control edge 3 may thus be designed insuch a way that it just corresponds to the sum of the axial extensionsof third and fourth openings 16, 17. The height of the control edge,i.e., its length in the axial direction, is thus minimized. In addition,supply port A is blocked and supply port B is connected to inlet port Pvia second annular groove 7.

LIST OF REFERENCE NUMERALS

-   1 central valve-   2 control piston-   3 first control edge-   4 second control edge-   5 third control edge-   6 annular groove, first annular groove-   7 second annular groove-   8 control piston cavity-   9 first end-   10 second end-   11 piston head-   12 piston head openings-   13 guiding sleeve-   14 first opening-   15 second opening-   16 third opening-   17 fourth opening-   18 fifth opening-   19 plastic extrusion-coating-   20 first transfer opening, annular channel-   21 second transfer opening-   22 third transfer opening-   23 fourth transfer opening-   24 spring seat-   25 spring-   26 central housing-   27 contact surface-   27 a check valve-   28 retaining ring-   29 flange-   P inlet port, pressure port-   T outlet port, tank port-   A supply port A-   B supply port B-   C supply port C

The invention claimed is:
 1. A central valve for a camshaft adjustingdevice, the central valve comprising: a control piston having a firstand a second control edge encompassing an annular groove; a valvehousing having a circumferential wall with circumferential wallopenings; and pressure medium paths running between an inlet port and anoutlet port, a settable profile of the pressure medium paths beingpredefined by the control edge geometry and the arrangement of theopenings, a set profile depending on a relative axial position of thecontrol piston, wherein—with regard to a central position of the controlpiston in each case—the first control edge is assigned to a firstopening and is designed to have a negative overlap with the firstopening in such a way that the first control edge does not cover thefirst opening on a side facing the second control edge, while the firstcontrol edge just closes the first opening—the first openingtransitioning to an annular channel on a valve housing side—on the sidefacing away from the second control edge, and the second control edge isassigned to a second opening and just closes the second opening on aside facing the first control edge; a third opening being situated at anoffset from the first opening in the circumferential direction; and thefirst control edge has a positive overlap with the third opening andjust completely closes the third opening on a side facing the secondcontrol edge.
 2. The central valve as recited in claim 1 wherein thefirst and second control edges are followed by a third control edgeencompassing a second annular groove together with the second controledge, a fourth opening being situated at an axial offset from the firstand third openings and a fifth opening from the first, second and thirdopenings.
 3. The central valve as recited in claim 2 wherein the fourthopening is situated at an offset with respect to the third opening inthe axial direction in such a way that the second control edge, which isdesigned to have a positive overlap with respect to the fourth opening,just completely unblocks the fourth opening on a side facing the thirdcontrol edge.
 4. The central valve as recited in claim 3 wherein thesecond and third control edges are designed to have a zero overlap withrespect to the second and fifth openings, respectively, so that thesecond and third control edges close the second and fifth openings,respectively.
 5. The central valve as recited in claim 4 wherein asupply port A is connected to the second opening, a supply port C isconnected to the third and fourth openings, and a supply port B isconnected to the fifth opening—facing outwardly in each case.
 6. Thecentral valve as recited in claim 5 wherein a pressure medium pathbetween the supply port C and the outlet port T may be formed via thethird opening, and a pressure medium path between the supply port C andthe inlet port P may be formed via the fourth opening, and the firstopening transitions to the annular channel, the supply port Aconnectable to an outlet port T with the aid of the annular channel. 7.The central valve as recited in claim 6 wherein in a first switchingposition, the supply ports A and C are connected to the inlet port P,and the supply port B is connected to the outlet port T; in a secondswitching position, the supply port C is connected to the inlet port P,and the supply ports A and B are blocked with the aid of at least one ofthe first, second and third control edges; in a third switchingposition, the supply ports B and C are connected to the inlet port P,and the supply port A is connected to the outlet port T; and in a fourthswitching position, the supply port C is connected to the outlet port T,and the supply port B is connected to the inlet port P, and the supplyport A is blocked with the aid of at least one of the first, second andthird control edges.
 8. The central valve as recited in claim 5 whereinthe central valve is usable in a camshaft adjusting device, including arotor which is coaxially and rotatably situated in relation to a stator,and which includes at least one locking piston C, with the aid of whichthe position of the rotor in relation to the stator may be fixed in adefined position.
 9. The central valve as recited in claim 8 wherein thecentral valve is able to communicate with pressure chambers A and B ofthe camshaft adjusting device via the supply ports A and B and with theat least one locking piston C via the supply port C, and the at leastone locking piston C is unlocked as a result of an application ofpressure medium.
 10. The central valve as recited in claim 3 wherein thethird control edge is followed by a fourth control edge, the fourthcontrol edge encompassing a third annular groove together with the thirdcontrol edge, a sixth opening being assigned to the third control edge.